1. Field of the Invention
The present invention relates to mechanical locks, primarily those used in vehicle seat positioners and recliners.
2. State of the Art
Mechanical locks allow parts to move relative to each other and to lock them together when necessary. Vehicle seats often use mechanical locks to control seat elevation and tilt angle and to lock the seat on horizontal rails to position the seat horizontally. Porter and Sember, U.S. Pat. No. 3,874,480 (1975), "Friction Brake Mechanism," Porter, U.S. Pat. No. 4,577,730 (1986), "Mechanical Lock," and Porter and Babiciuc, U.S. Pat. No. 5,219,045 (1993), "Linear Mechanical Lock with One-Piece Lock Housing," are examples.
These locks usually rely on a translating rod within an elongated, tubular housing. Either the housing or the rod attaches to a stationary vehicle part, and the other end attaches to a vehicle part. A coil spring, which is fixed relative to the housing, encircles the rod. The spring's normal inside diameter is slightly less than the rod's outside diameter. A release lever acting on the coil spring's free end unwinds or uncoils the spring slightly, which increases the spring's inside diameter enough to release the rod.
These mechanical locks can have problems. The rod is circular, so it can rotate slightly within the housing. Slight rotation can degrade the locking characteristics and damage the lock. Much force is needed to overcome the spring tension of the locking springs. Also, the mechanism that uncoils the springs must move far, which slows locking and unlocking of the lock. Buckling under high loads can also be a problem. Last, the prior art locks require complex assembling, which adds to their costs.